Winding core

Abstract

With a view to making it possible to load a cassette onto a to-be-loaded body in a slack-free good condition of a web accommodated in the cassette, preventing the entry of dust into engaging grooves after the loading of the cassette, and permitting the loading of only such a cassette as is suitable for the loading, there is provided a winding core in a ribbon cassette which accommodates an ink ribbon in a wound-up state, the winding core having a plurality of engaging grooves formed circumferentially in its peripheral surface for engagement with a plurality of engaging projections formed circumferentially at equal intervals on an outer peripheral surface of a winding bobbin of the to-be-loaded body onto which the cassette is to be loaded, the engaging grooves each having side engaging portions for engagement with side faces of each engaging projection and an upper engaging portion for engagement with an axial tip face of each engaging projection in an abutted or covering relation thereto.

We claim: 
     
       1. A winding core which accommodates a web in a wound-up state, said winding core having a winding direction, said winding core having a plurality of engaging grooves formed circumferentially in its inner peripheral surface for engagement with a plurality of engaging projections formed circumferentially at equal intervals on an outer peripheral surface of a winding bobbin of a carriage onto which a cassette is to be loaded, said engaging grooves each having side engaging portions for engagement with side faces of each said engaging projection and an upper engaging portion for engagement with an axial tip face of each said engaging projection in an abutted or covering relation thereto; said engaging grooves being formed in such a manner that an engaging groove having an engaging groove insertion side at one axial end of the winding core and an engaging groove having an engaging groove insertion side at the opposite end of the winding core are alternately arranged circumferentially at equal intervals; and   wherein an engaging guide portion is contiguous to each of said side engaging portions of each said engaging groove at an insertion-side end portion of the engaging groove, said engaging guide portion being formed as a slant face for causing each said engaging projection of the winding bobbin to slide in a relative manner and guiding it into any of the engaging grooves of the winding core.   
     
     
       2. A winding core according to claim 1, wherein said engaging guide portions which connect the insertion-side end portions of engaging grooves having insertion sides at the same end portion of the winding core also serve as the upper engaging portion of an engaging groove having an insertion side at the opposite end portion. 
     
     
       3. A winding core according to claim 2, wherein, out of said side engaging portions of each said engaging groove, the side engaging portion formed on the winding direction side of the winding core is shorter than the side engaging portion formed on the side opposite to the winding direction of the winding core, and said engaging guide portions are each formed as a slant face between the insertion-side end of a side engaging portion formed on the winding direction side of the winding core and the insertion-side end of a side engaging portion formed on the side opposite to the core winding direction of an adjacent engaging groove having an insertion side in the same direction. 
     
     
       4. A winding core according to claim 2, wherein, out of said side engaging portions, the side engaging portion formed on the winding direction side of the winding core is shorter than the side engaging portion formed on the side opposite to the winding direction of the winding core, the engaging guide portion of each said side engaging portion is formed at an insertion-side end of the side engaging portion so as to expand from the associated engaging groove, and a tip end of the engaging guide portion contiguous to the side engaging portion formed on the core winding direction side of each engaging groove is connected with a tip end of the engaging guide portion contiguous to the side engaging portion formed on the side opposite to the core winding direction of an adjacent engaging groove. 
     
     
       5. A winding core according to claim 4, wherein said upper engaging portion of each said engaging groove is in a steepled shape.